-------- Original Message --------
Subject: Re: Quota limit question
From: Christian Robottom Reis <k...@canonical.com>
To: Duncan <1i5t5.dun...@cox.net>
Date: 2015年03月07日 05:44
Just as a follow-up, I upgraded btrfs-tools and the kernel again. I
currently have a filesystem which reports 1G exclusive use:
root@riff# btrfs qg show -r -e /var -p -c
qgroupid rfer excl max_rfer max_excl parent child
-------- ---- ---- -------- -------- ------ -----
0/261 1.52GiB 1.01GiB 0.00B 100.00GiB --- ---
It's recommended to sync the btrfs before 'qg show' command, since quota
tree is not updated until commit transaction.
This filesystem reports over quota, and removing the quota fixes that:
root@riff# touch x
touch: cannot touch ‘x’: Disk quota exceeded
root@riff# btrfs qg limit -e
none 261 /var
root@riff# touch x
root@riff#
So at the moment quotas are pretty much unusable in kernel 3.18.6/tools
3.18.2, at least for my use case, and that's a bit surprising since
there isn't anything very interesting about it (other than it contains a
bunch of lxc-cloned rootfs).
Yes, Btrfs really has some problems, from yours to other annoying
incorrect values.
[Some guess]
For your case, I'm afraid your reserved space in your qgroup takes too
much space, and it's definitely a bug. Maybe some btrfs_qgroup_reserve()
leaking?
[Reproducer]
Would you please describe your workload? Or some easy-to-reproduce scripts?
[Image dump/debug tree]
Another one which may help is your btrfs-debug-tree output on your quota
tree.
You can dump it by "btrfs-debug-tree -t 8 <DEVICE>".
Or full disk metadata dump by "btrfs-image -c9 <DEVICE>"
Thanks,
Qu
I've proactively added Yang who has submitted a few patches on quota
checking recently just to let me know if he thinks that this should be
fixed with a trunk kernel, or if he'd like to investigate or consider
this further. Thanks!
On Wed, Dec 24, 2014 at 03:52:41AM +0000, Duncan wrote:
Christian Robottom Reis posted on Tue, 23 Dec 2014 18:36:02 -0200 as
excerpted:
On Tue, Dec 16, 2014 at 11:15:37PM -0200, Christian Robottom Reis wrote:
# btrfs qgroup limit 2000m 0/261 . && touch x touch: cannot touch
‘x’: Disk quota exceeded
The strange thing is that it doesn't seem to be actually out of space:
# btrfs qgroup show -p -r -e /var | grep 261
0/261 1111810048 391114752 2097152000 0 ---
Replying to myself as I had not yet been subscribed in time to receive a
reply; I just upgraded to 3.18.1 and am seeing the same issue on the
same subvolume (and on no others).
Looking at the thread here on gmane.org (list2news and list2web gateway),
it appears my reply was the only reply in any case, and it was general as
I don't run quotas myself.
Basically I suggested upgrading, as the quota code as some rather huge
bugs in it (quotas could go seriously negative!) with the old versions
you were running. But you've upgraded at least the kernel now (userspace
you didn't say).
Here's a link to the thread on the gmane web interface for completeness,
but the above about covers my reply, as I said the only one until your
thread bump and my reply here, so there's not much new there unless
someone posts further followups to this thread...
http://comments.gmane.org/gmane.comp.file-systems.btrfs/41491
--
Duncan - List replies preferred. No HTML msgs.
"Every nonfree program has a lord, a master --
and if you use the program, he is your master." Richard Stallman
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